This invention relates to a temperature controller utilizing a thermocouple having hot and cold junctions as a temperature detecting means.
A temperature controller utilizing a thermocouple detects and controls the temperature of a measuring object in accordance with the thermoelectric voltage which is generated by the thermocouple according to the temperature difference between a measuring junction positioned adjacent to the measuring object such as a furnace and a reference junction or junctions, known as cold junction or junctions, positioned near the housing of the temperature controller. It is well known that some temperature compensation for the cold junction is required for accurate measurement, since the ambient temperature around the cold junction often varies. A temperature controller heretofore used is provided with a cold junction temperature compensation element which is fixed to a terminal cover, which in turn is fixed to the housing of the temperature controller. This controller is described in Omron Tatusi Electronics Co., Catalog No. ESA-002, entitled "Omron Solid State Temperature Controller", July, 1977. However, the thus constructed temperature controller is not structurally copact, and is expensive to manufacture.
Therefore, it is an object of this invention to provide a temperature controller which is accurately operable in spite of fluctuations in ambient temperature. It is another object of this invention to provide a temperature controller which is compact and can be manufactured at low cost. The temperature controller of this invention is characterized in that a cold junction compensation element is located in a hollow projecting guide-pin of a plug having a plurality of projecting terminal-pins surrounding the hollow guide-pin, the internal space of the hollow guide-pin communicating with the ambient atmosphere.